Gas-Phase Ozone Oxidation of Monoterpenes: Gaseous and ...
Gas-Phase Ozone Oxidation of Monoterpenes: Gaseous and ...
Gas-Phase Ozone Oxidation of Monoterpenes: Gaseous and ...
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GAS-PHASE OZONE OXIDATION OF MONOTERPENES 221<br />
Further differentiation among the three isomers is impossible on the basis <strong>of</strong> CI <strong>and</strong><br />
EI mass spectra. Figure 2-P 6 shows ion fragment patters using pinalic-4-acid as an<br />
example. Compound P 7 is identified as cis-pinonic acid, <strong>and</strong> the identification has<br />
been confirmed by comparison with an authentic st<strong>and</strong>ard. The CI mass spectrum<br />
<strong>of</strong> its derivative is shown in Figure 2-P 7 . Compound P 8 is tentatively identified<br />
as hydroxy norpinonic acid, with a MW <strong>of</strong> 525 for its derivative (Figure 2-P 8 ).<br />
Compound P 9 is tentatively identified as hydroxy pinonic acid, with a MW <strong>of</strong> 539<br />
for its derivative (Figure 2-P 9 ).<br />
Some <strong>of</strong> the products observed here have been reported in previous studies.<br />
Nopinone has long been identified as a major product in the β-pinene/O 3 reaction<br />
(Hull, 1981; Hatakeyama et al., 1989; Grosjean et al., 1993, Hakola et<br />
al., 1994). Using GC/MS <strong>and</strong> nuclear magnetic resonance (NMR) analyses, Hull<br />
also positively identified 3-hydroxy-pina ketone <strong>and</strong> 3-oxo-pina ketone <strong>and</strong> had<br />
indirect evidence for the formation <strong>of</strong> 1-hydroxy-pina ketone. Products that are<br />
reported here for the first time include pinic acid, norpinic acid, 2,2,-dimethyl-3-<br />
formyl-cyclobutyl methanoic acid, norpinonic acid <strong>and</strong> its isomers, pinonic acid,<br />
hydroxy norpinonic acid, hydroxy pinonic acid, <strong>and</strong> 2,2-dimethyl-cyclobutane-1,3-<br />
dicarboxaldehyde.<br />
3.2. PRODUCTS FROM OZONE OXIDATION OF SABINENE<br />
Carbonyl bearing products <strong>of</strong> the sabinene/O 3 reaction are shown in Figure 3(a),<br />
<strong>and</strong> OH/COOH bearing products are shown in Figure 3(b). Table V lists the MWs<br />
<strong>and</strong> chemical structures <strong>of</strong> these products. Most products are analogous to those<br />
identified in the β-pinene/O 3 reaction, <strong>and</strong> their methane CI mass spectra are similar<br />
to those in the β-pinene/O 3 reaction. The CI mass spectra are given only for<br />
the products unique in the sabinene/O 3 reaction (Figure 4). Interested readers can<br />
get from us the mass spectra data for those analogous products.<br />
Among the products, compound S 1 ,S 2 ,<strong>and</strong>S 3 contain only OH/COOH groups<br />
(type 2 compounds). Compound S 1 is tentatively identified as norsabinic acid on<br />
the basis <strong>of</strong> that it shows a MW <strong>of</strong> 316 for its derivative, <strong>and</strong> elutes at an earlier retention<br />
time than that <strong>of</strong> norpinic acid. The CI spectrum <strong>of</strong> compound S 2 indicates a<br />
MW <strong>of</strong> 330 for its TMS derivative. S 2 elutes from the GC column earlier than pinic<br />
acid. It is tentatively identified as sabinic acid, the analogue <strong>of</strong> pinic acid derived<br />
from sabinene. Compound S 3 is pinic acid, confirmed by authentic st<strong>and</strong>ard. The